Pressure roll

ABSTRACT

A pressure roll having a fixed carrier and a rotating elastically deformable roll jacket that cooperates with a counter-roll and that is supported on the carrier via a hydrostatic support arrangement. The roll jacket has an inner surface that is movably guided in the peripheral direction over a concave support surface. The roll jacket is executed with a wall that is flexible in the radial direction and can conform to the counter-roll over a pressure zone whose width dimension in the peripheral direction is adjustable within a range of at least 8 mm to circa 40 mm. Furthermore, the roll jacket consists at least partially of an electrically conductive material in order to prevent an uncontrolled electrostatic charging of the jacket surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a pressure roll in accordance with the preambleof claim 1.

Pressure rolls of the named kind are often used in printing machines, inparticular in rotogravure printing machines, as pressure rolls whichcooperate with a printing cylinder in each case. A known pressure rollof this kind is executed with a highly elastic roller jacket in the formof a hollow cylinder of polyurethane or an elastomer which permitsbending deflections transverse to its longitudinal axis and has across-section of substantially stable shape (K. A. Springstein "DieSpitzenqualitat im Tiefdruck hangt auch vom Presseursystem ab" (topquality in rotogravure printing also depends on the pressing system),reprint from the trade journal "Deutscher Drucker", No. 28 dated 15 Sep.1988). The roll jacket of the known pressure roll is pressed against theprinting cylinder via hydrostatic support elements, with the formationof a substantially linear pressing zone with a relatively slight extentin the peripheral direction of the roll jacket. In that arrangement thepressing zone can be widened in a deflection zone which arises through acompression of the roller jacket to such an extent that a printing zonewith a width of approximately 10 to 18 mm is formed. The ink applied tothe printing cylinder in a printing machine must in each case betransferred to the matter to be printed in the region of this printingstrip.

In order to ensure a reliable ink transfer at a printing speed of, forexample, 15-20 m/sec, it is known to provide the roll jacket with anindirect or direct electrostatic printing aid (ESA). These knownprinting aids are, however, relatively complicated and expensive andmaintenance-intensive systems. To achieve a high print quality, it isfurthermore essential that the width of the printed strip or bandremains constant during the printing process. In previous pressure rollsof the named kind, and as a result of load changes in the roll zone incertain cases, e.g. when printing printed matter with longitudinalsections of differing thickness, correspondingly differing tangentialforces can act on the individual longitudinal sections, with it beingpossible for the respective effective width of the printing strip tovary and thus for distortions of the printed matter to arise, throughwhich the quality of the ink transfer can be impaired.

SUMMARY OF THE INVENTION

The object of the invention is to provide a further developed pressureroll suitable for various applications of the initially named kind whichenables the formation of a pressure zone with a constant gap width thatis adjustable independently of the respective loading and which permitsan intentional influencing of the dwell time of a web of materialpassing through the pressing position, which can be used for atreatment, and which ensures a treatment of the web of materialtravelling through the pressure zone that is free from electrostaticauxiliary devices, or can at least be achieved with reducedelectrostatic charging, even at a running speed of 20 m/sec or more.

Through the flexibility in the radial direction of the roll jacket ofthe press roll designed in accordance with the invention, a press gapcan be achieved between it and the counter-roll whose width, incomparison with previous embodiments, can be freely chosen within alarger peripheral region of the counter-roll, and this width can amountto a multiple of the gap widths possible with previous embodiments.Accordingly, a low-distortion guidance of the material web--e.g. a paperor textile web--can be achieved which is independent of the respectivestressing, and/or its dwell time in the press gap can be lengthened tosuch an extent that the use of electrostatic auxiliary devices issuperfluous or that their use can at least be largely restricted. Thepressure roll executed in accordance with the invention is particularlyadvantageous for printing machines since, on the one hand, e.g. indecorative printing, it ensures a constant width of the printed stripuninfluenced by changes in load even at gap widths of from 8 to 10 mmand, on the other hand, enables a corresponding lengthening of the dwelltime of the printing ink in the printing zone which can be utilized forthe ink transfer. The lengthened dwell time thereby results inadditional freedom for the use of novel ink systems which, for example,require a longer drying time than previous systems. The execution of thepressure roll in accordance with the invention also permits acorresponding lengthening of the dwell time of a textile web to becompressed and/or to be provided with a structure, e.g. an embeddedstructure, in the press gap.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partial, section view of a printing machine pressure roll inaccordance with the invention which cooperates with a printing cylinder;

FIG. 2 is a section of the pressure roll in accordance with theinvention corresponding to the line II--II in FIG. 1;

FIG. 3 is a partial section of the pressure roll corresponding to theline III--III in FIG. 1;

FIG. 4 is an enlarged detail view of FIG. 2; and

FIG. 5 is a partial view of the detail corresponding to the arrow V inFIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

The pressure roll 1 of FIGS. 1 and 2 is arranged as a pressure roll in anon-illustrated printing machine, in the present example in arotogravure printing machine, and cooperates with a counter-roll 2,illustrated as a forming cylinder of the printing machine, in a printingzone 3 through which there is guided a paper web 4 on which printing isto take place. The pressure roll 1 comprises, as is, for example, knownfrom the initially cited reference, a fixed carrier 5 and a roll jacket6 which can be rotated about the latter and consists of an elasticallydeformable material, e.g. of a plastic. The roll jacket 6 of thepressure roll 1 in accordance with the invention consists at leastpartially of an electrically conductive material, in the exampleillustrated of an elastomer, which is executed with an insulating innerlayer and an outer layer formed as a "semiconductor". The elastomer canalso be reinforced, e.g. by a fabric.

As seen in FIG. 1 the carrier 5 is secured at both its ends by means ofbearing spigots 7 in holder blocks 8 which are each mounted on anon-illustrated carrier of the printing machine. Support rings 13 arerotatably journalled on the bearing spigots 7 via bearing arrangements10 which contain roller bearings 11 and sealing means 12. The supportrings 13 are executed with ring-shaped grooves 14 in which the ends 6aof the roll jacket 6 are each secured by means of a clamping ring 15.

The carrier 5 is executed with a longitudinal groove 16 in which a rowof piston-shaped guide elements 17 of a hydrostatic support arrangement20 are mounted in a fixed position. The support arrangement 20 containsa corresponding number of cylinder-shaped support elements 18, 18a eachof which movably and sealingly cooperates with one of the guide elements17 and bounds a pressure space 21. The support arrangement 20 furthercontains a strip-shaped support part 22 which is coupled to all supportelements 18, 18a and extends substantially over the working length ofthe roll jacket 6 and which is secured to the support elements 18 bymeans of screws 23.

As is seen in FIGS. 2 and 3 in particular, the roll jacket 6 is executedwith a wall which is flexible in the radial direction and permits theroll jacket 6 to conform with the counter-roll 2 over a section of itsperiphery whose width dimension in the peripheral direction is, forexample, 20 mm. Depending on the material and the wall thickness T ofthe roll jacket 6 a multiple of this width measurement can be achieved.On the other hand it can also be worthwhile, e.g. for decorativeprinting, to bring the roll jacket 6 and the counter-roll 2 togetherover a peripheral section with a substantially smaller width dimension,e.g. 8 to 10 mm.

The support part 22 is executed with a concave support surface 24 whoseform is determined by a radius R1 in accordance with FIG. 4 whichcorresponds substantially to the sum of the radius R of the counter-roll2 and the wall thickness T of the roll jacket 6. In order to ensure theuniversal use of the pressure roll 1, which is to cooperate withcounter-rolls 2 of differing diameters or radii R and R', it isexpedient for the radius R1 of the support surface 24 to be matched tothe radius R of the smallest counter-roll 2 to be used. On at least onelongitudinal side of the support part 22, and on both sides as shown inthe drawing, two neighboring, convex guide surfaces 25 are associatedwith the concave support surface 24. Their shape is determined by aradius R2 which is equal to or less than the radius of a cylindricalsurface determined by the inner surface of the roll jacket 6. Theseconvex guide surfaces 25 facilitate the introduction of the roll jacket6 into the pressure zone formed between the support surface 24 and thecounter-roll 2 during its rotational movement.

The support surface 24 of the support part 22 is provided withhydrostatic bearing pockets 26 for a hydrostatic lubrication system. Thebearing pockets 26 are connected to the pressure spaces 21 of thesupport elements 18 through restrictor bores 27 provided in the screws23. The pressure spaces 21 are each connected via bores 28 and 29passing through the guide part 17 and the carrier 5 respectively to asupply system 30 for a hydraulic pressure fluid. The supply system 30 isarranged in a central longitudinal bore 31 of the carrier 5 andindicated in the example illustrated by a tubular line 32 passingthrough the longitudinal bore 31 and connected to a non-illustratedsource of the hydraulic fluid.

In addition to a compensation of the bending deflection, a substantiallyconstant hydrostatic lubrication gap is maintained between the supportsurface 24 and the inner surface of the roll jacket 6 through thesupport arrangement 20 and the described design of the support part 22.As can be seen in particular in FIGS. 3 and 4, hydrostatic bearingpockets 33 through which a lateral stabilization of the support part 22can be achieved can also be formed in the guide surfaces 25. The bearingpockets 33 are connected to the pressure spaces 21 of thecorrespondingly positioned support elements 18a through restrictor bores34 arranged distributed over the length of the support part 22.

As can be seen from FIGS. 1 and 5 in particular, the bearing pockets 26and 33 are each bounded in the longitudinal direction of the supportpart 22 by bridge parts or web portions 35 of the guide surface 24.Instead of the illustrated embodiment with a plurality of bearingpockets 26 and 33, an embodiment can also be provided with a singlebearing pocket 26 extending over the length of the support part 22and/or with correspondingly extending bearing pockets 33 which are onlybounded by the bridge parts 35 formed in the end sections of the guidepart 22.

An embodiment is also possible in which the support part 22 extends onlyover a part of the working length of the roll jacket 6 or only over someof the support elements 18 respectively. A plurality of support parts 22arranged next to one another in the longitudinal direction can also beprovided, each connected to some of the support elements 18.Furthermore, support elements 18 can also be executed with concavesupport surfaces 24 and cooperate directly with the roll jacket 6, inwhich case the provision of a strip-shaped support part 22 issuperfluous. In order to influence the pressure distribution, thebearing pocket or the individual bearing pockets 26 and 33 of thesupport arrangement 20 can also be combined with a non-illustratedapparatus for hydrodynamic pressure assistance, whereby the bearingpockets 26 can be executed with smaller dimensions.

The carrier 5 is provided with at least one guide part, in theillustrations with five guide parts 36 in the form of support carriersfor the inner surface of the roll jacket 6, which are displaced in theperipheral direction with respect to the support arrangement 20. Theguide parts 36 are supported only in the end regions of the carrier 5 sothat they permit bending deflections of the carrier 5 and at the sametime ensure a form-stable guidance of the roll jacket 6. In a different,non-illustrated embodiment, corresponding guide parts 35 can be coupledto the bearing arrangements 10. Instead of support carriers, a guidepart, e.g. a trough-like guide part, can also be provided which extendsover a portion of the periphery of the inner surface of the roll jacket6.

A pressure roll 1 in accordance with FIGS. 1 and 2 can also be providedas the working roll of a non-illustrated apparatus for treating, e.g.compressing or embossing, a material web, such as a cloth or a non-wovenarticle. A guide roll with a smooth jacket surface or an embossing rollwith a correspondingly structured surface can be provided as acounter-roll 2. Accordingly, in an embodiment of this kind the dwelltime of the material web in the effective zone can also be lengthened,an uncontrolled electrostatic charging of the jacket surface can beavoided, and thus the processing of sensitive textile webs, e.g. thosecontaining a plastic component, can be simplified.

In summary, the invention can be described as follows:

The pressure roll has a fixed carrier and a rotating elasticallydeformable roll jacket which cooperates with a counter-roll and which issupported on the carrier via a hydrostatic support arrangement and whoseinner surface is movably guided in the peripheral direction over aconcave support surface. The roll jacket is executed with a wall whichis flexible in the radial direction and can conform to the counter-rollover a pressure zone whose width dimension in the peripheral directionis adjustable within a range of at least 8 mm to circa 40 mm.Furthermore, the roll jacket consists at least partially of anelectrically conductive material in order to prevent an uncontrolledelectrostatic charging of the jacket surface. Accordingly, a treatmentof a material web can be achieved which is free of electrostaticauxiliary devices, or can at least be accomplished with reducedelectrostatic charging, e.g. a simplified transfer of printing ink to aprinting material.

What is claimed is:
 1. A pressure roll comprising:a fixed carrierincluding at least one guide surface that includes a support surface; aroll jacket that rotates about the fixed carrier and is formed of anelastically deformable material, the roll jacket comprising:anelectrically conductive layer, and an inner surface having asubstantially circular cylindrical shape, wherein the roll jacket iscapable of moving along the support surface and the guide surface at theinner surface; and a counter-roll that forms a pressure zone inconjunction with the roll jacket, the pressure zone having an adjustablewidth.
 2. The pressure roll of claim 1 wherein the support surfacepossesses a concave configuration in the circumferential direction ofthe roll jacket.
 3. The pressure roll of claim 1 wherein the pressurezone width is adjustable in a range of 8 mm to 40 mm.
 4. The pressureroll of claim 1 wherein the support surface has a radius thatcorresponds substantially to the sum of the radius of the counter-rolland the thickness of the roll jacket.
 5. The pressure roll of claim 1further comprising at least one convexly shaped guide surface associatedwith the support surface, the at least one convexly shaped guide surfacebeing adjacently disposed along a peripheral direction, the shape of theat least one convexly shaped guide surface being determined by a radiusthat is equal to a radius of a cylindrical surface determined by theinner surface of the roll jacket.
 6. The pressure roll of claim 1further comprising at least one convexly shaped guide surface associatedwith the support surface, the at least one convexly shaped guide surfacebeing adjacently disposed along a peripheral direction, the shape of theat least one convexly shaped guide surface being determined by a radiusthat is less than a radius of a cylindrical surface determined by theinner surface of the roll jacket.
 7. The pressure roll of claim 1further comprising a support arrangement that contains a plurality ofhydrostatic support elements adjacently arranged in a longitudinaldirection of the fixed carrier in which the support surface is formed onat least one support part that is braced against the fixed carrier viathe hydrostatic support elements.
 8. The pressure roll of claim 7wherein the support part is in the form of a support strip that extendssubstantially over a determinable working length of the roll jacket. 9.The pressure roll of claim 1 wherein the support surface includes atleast one hydrostatic bearing pocket that is bounded in the longitudinaldirection of the fixed carrier by at least two bridge parts of thesupport surface.
 10. The pressure roll of claim 1 wherein the guidesurface includes at least one hydrostatic bearing pocket that is boundedin the longitudinal direction of the fixed carrier by at least twobridge parts of the guide surface.
 11. The pressure roll of claim 1wherein the fixed carrier further includes at least one guide part forthe inner surface of the roll jacket that is arranged to be displacedwith respect to the support arrangement in the peripheral direction andextends over a portion of its longitudinal extent.
 12. The pressure rollof claim 11 wherein the guide part is in the form of a support carrierthat is supported at the end regions of the fixed carrier and permitsbending deflections of the fixed carrier.
 13. The pressure roll of claim1 wherein the electrically conductive layer is an outer layer, and theroll jacket further comprises an inner insulating layer.
 14. A printingmachine comprising a pressure roll device, the pressure roll devicecomprising:a fixed carrier including at least one guide surface thatincludes a support surface; a roll jacket that rotates about the fixedcarrier and is formed of an elastically deformable material, the rolljacket comprising:an electrically conductive layer, and an inner surfacehaving a substantially circular cylindrical shape, wherein the rolljacket is capable of moving along the support surface and the guidesurface at the inner surface; and a counter-roll that forms a pressurezone in conjunction with the roll jacket, the pressure zone having anadjustable width.
 15. The printing machine of claim 14 wherein theprinting machine is a rotogravure printing machine.